Self-organised Fept Nanoparticle Arrays, Compacted Powders and Fept Nanoparticles Embedded on Sio2 Matrix

Monodispersed magnetic nanoparticles self-organised into superlattices onto a substrate are considered to be of real interest in the development of future magnetic storage systems due to their potential ultra-high storage density, higher than 1 Tbit/cm [1]. These particles are coated by organic acids as oleic acid which act as surfactant layer and avoid coalescence and prevent possible growth of secondary particles [2]. Nevertheless, some technical problems should be overcome before actual use for applications. One of them is that as-prepared samples have a chemically disordered fcc structure, A1 phase, with low anisotropy. To achieve the phase transition from fcc to L10 in FePt nanoparticles, the samples have to be subjected to thermal treatments [1]. During such annealing, and before the structural transition, different reactions take place in the particle surface, and the surfactant protecting the FePt particles is thermally decomposed. The A1-L10 phase transformation is accompanied by a sintering process, since the steric barrier between particles is removed [3].